Photosensitive resin composition

Abstract

This photosensitive resin composition comprises a thermoplastic elastomer (A), a liquid farnesene rubber (B), an ethylenic unsaturated compound (C), and a photoinitiator (D).

Description

Technical Field

[0001] The present invention relates to a photosensitive resin composition and a flexographic printing plate using the photosensitive resin composition.

Background Art

[0002] The photosensitive resin composition used for a flexographic printing plate generally contains a thermoplastic elastomer, a photopolymerizable unsaturated monomer, a plasticizer such as a conjugated diene rubber, and a photoinitiator (see, for example, Patent Documents 1 to 4).

[0003] The constituent for a flexographic printing plate generally uses a polyester film or the like as a support, and a photosensitive layer made of the above photosensitive resin composition is provided thereon. Further, if necessary, a slip layer or a protective layer is provided on the photosensitive layer for the purpose of smoothing the contact with a negative film. To produce a flexographic printing plate from such a constituent for a flexographic printing plate, generally, first, ultraviolet exposure is performed on the entire surface through the support (back exposure) to provide a thin and uniform cured layer at the support interface of the photosensitive layer, and then, image exposure (relief exposure) is performed on the surface of the photosensitive layer with ultraviolet light through a negative film covering the upper part of the photosensitive layer. Thereafter, it is manufactured by washing away the unexposed portion of the photosensitive layer with a developer, or by performing post-treatment exposure after heating and melting and then absorbing and removing with an absorption layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

[0005] In flexographic printing, multiple printing plates are typically formed from a single negative film. Since the photosensitive layer is generally adhesive, if the negative film is placed directly on the photosensitive layer, the negative film may be damaged and unusable when peeled off the layer after image exposure. Therefore, the photosensitive layer needs to have low tack so that the negative film can be easily peeled off and reused. However, the photosensitive layer using the photosensitive resin compositions described in Patent Documents 1 to 4 above cannot achieve sufficiently low tackiness. Furthermore, the printing plate is required to suppress the adhesion of dust during printing and tearing of the printed material, and to have excellent printability. In addition, the printing plate is required to have minimal changes in physical properties over time and excellent printability stability.

[0006] Therefore, the first objective of the present invention is to provide a photosensitive resin composition that has low tackiness before and after curing, and low extraction rate after curing.

[0007] Furthermore, a second objective of the present invention is to provide a photosensitive resin composition that maintains a low extraction rate after curing while exhibiting low tackiness before and after curing. [Means for solving the problem]

[0008] As a result of diligent research to solve the above problems, the inventors of the present invention have found that the problems can be solved by including liquid farnesene rubber in the photosensitive resin composition, and have completed the present invention. In other words, the present invention is as follows.

[0009] [1] A photosensitive resin composition comprising a thermoplastic elastomer (A), a liquid farnesene rubber (B), an ethylenically unsaturated compound (C), and a photoinitiator (D). [2] The photosensitive resin composition according to [1], wherein the thermoplastic elastomer (A) is at least one selected from the group consisting of styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-(ethylene-butylene)-styrene block copolymer, and styrene-(ethylene-propylene)-styrene block copolymer. [3] The photosensitive resin composition according to [1] or [2] above, wherein the content of monomer units derived from farnesene in the liquid farnesene rubber (B) is 10% by mass or more. [4] The photosensitive resin composition according to any one of [1] to [3] above, wherein the number average molecular weight of the liquid farnesene rubber (B) is 7,000 to 150,000. [5] The photosensitive resin composition according to any one of [1] to [4] above, wherein the glass transition temperature of the liquid farnesene rubber (B) is -60°C or lower. [6] The photosensitive resin composition according to any one of [1] to [5] above, wherein the vinyl content of the liquid farnesene rubber (B) is 5 to 80 mol%. [7] The photosensitive resin composition according to any one of [1] to [6] above, wherein the thermoplastic elastomer (A) is at least one selected from the group consisting of styrene-butadiene-styrene block copolymer and styrene-isoprene-styrene block copolymer. [8] The photosensitive resin composition according to [7], wherein the thermoplastic elastomer (A) comprises a styrene-butadiene-styrene block copolymer. [9] The photosensitive resin composition according to [7], wherein the thermoplastic elastomer (A) comprises a styrene-isoprene-styrene block copolymer.

[10] The photosensitive resin composition according to any one of [1] to [9] above, wherein the content of the thermoplastic elastomer (A) is 40 to 87.9% by mass, the content of the liquid farnesene rubber (B) is 10 to 40% by mass, the content of the ethylenically unsaturated compound (C) is 2 to 30% by mass, and the content of the photoinitiator (D) is 0.1 to 10% by mass.

[11] A flexographic printing plate having a photosensitive layer composed of the photosensitive resin composition according to any one of [1] to

[10] above.

[12] A laminate having a layer composed of the photosensitive resin composition according to any one of [1] to

[10] above. [Advantages of the Invention]

[0010] According to the present invention, it is possible to provide a photosensitive resin composition having low tackiness before and after curing and a low extraction rate after curing. [Modes for Carrying Out the Invention]

[0011] Hereinafter, an example of an embodiment of the present invention will be described. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following description. Also, in this specification, although preferred forms of the embodiment are shown, those obtained by combining two or more of the individual preferred forms are also preferred forms. For matters shown in a numerical range, when there are several numerical ranges, the lower limit value and the upper limit value thereof can be selectively combined to form a preferred form. In this specification, when a numerical range of "XX to YY" is described, it means "XX or more and YY or less".

[0012] [Photosensitive Resin Composition] The photosensitive resin composition according to the present invention is characterized by containing a thermoplastic elastomer (A), a liquid farnesene rubber (B), an ethylenically unsaturated compound (C), and a photoinitiator (D).

[0013] [Thermoplastic Elastomer (A)] The thermoplastic elastomer (A) used in the present invention is a polymer that can be plasticized and molded at high temperatures and exhibits properties as a rubber elastic body at normal temperatures. The thermoplastic elastomer (A) is not particularly limited, but a styrene block copolymer is preferred from the viewpoints of easy availability and moldability of the printing plate. A styrene-based block copolymer is a block copolymer having at least a polymer block consisting mainly of styrene-derived structural units (hereinafter sometimes referred to as "polymer block (a)") and a polymer block consisting of conjugated diene-derived structural units (hereinafter sometimes referred to as "polymer block (b)"). The polymer block consisting mainly of styrene-derived structural units preferably contains 90% by mass or more of styrene-derived structural units, more preferably 95% by mass or more, and even more preferably consists only of styrene-derived structural units. The polymer block consisting mainly of styrene-derived structural units may also contain structural units derived from styrene monomers other than styrene. Examples of styrene monomers other than styrene include α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, 2,4-dimethylstyrene, vinylnaphthalene, vinylanthracene, and the like. On the other hand, examples of conjugated dienes in polymer blocks composed of structural units derived from conjugated dienes include butadiene, isoprene, chloroprene, 2,3-dimethylbutadiene, 1,3-pentadiene, and 1,3-hexadiene. Among these, butadiene and isoprene are preferred from the viewpoint of availability. The above monomers and conjugated dienes may be used individually or in combination of two or more. In the above-mentioned styrene-based block copolymer, it is preferable that the olefinic double bonds are not hydrogenated, however, 10 mol% or less of the carbon-carbon double bonds of the structural units derived from the conjugated diene may be hydrogenated.

[0014] The content of polymer block (a) in the above styrene-based block copolymer is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of effectively reducing tackiness. From the viewpoint of moldability, it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. In addition, the content of the polymer block (b) in the styrene-based block copolymer is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 65% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, still more preferably 85% by mass or less.

[0015] Specific examples of the thermoplastic elastomer (A) include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-(ethylene-butylene)-styrene block copolymer (SEBS), styrene-(ethylene-propylene)-styrene block copolymer (SEPS), and the like. Among them, from the viewpoints of the moldability of the printing plate and the image reproducibility, the thermoplastic elastomer (A) is preferably at least one selected from the group consisting of a styrene-butadiene-styrene block copolymer and a styrene-isoprene-styrene block copolymer. In one embodiment, the thermoplastic elastomer (A) includes a styrene-butadiene-styrene block copolymer. In another embodiment, the thermoplastic elastomer (A) includes a styrene-isoprene-styrene block copolymer. This another embodiment is suitable when it is desired to create a printing plate that is thinner and harder than a normal printing plate. The thermoplastic elastomer (A) may include a styrene-butadiene-styrene block copolymer and a styrene-isoprene-styrene block copolymer. Further, the thermoplastic elastomer (A) may be a styrene-butadiene-styrene block copolymer and a styrene-butadiene / isoprene-styrene block copolymer. Here, "butadiene / isoprene" means a copolymer block having butadiene and isoprene as constituent monomers.

[0016] Examples of commercially available thermoplastic elastomers (A) include Kraton D (product name) from Kraton Polymers, Inc., Toughprene (registered trademark) (product name) and Asaprene (registered trademark) T (product name) from Asahi Kasei Chemicals Corporation, JSR TR (product name) and JSR SIS (product name) from JSR Corporation, Quintac (registered trademark) (product name) from Nippon Zeon Co., Ltd., and Hybrar 5125 (product name) and Hybrar 5127 (product name) from Kuraray Co., Ltd.

[0017] The weight-average molecular weight (Mw) of the thermoplastic elastomer (A) is not particularly limited, but is preferably 10,000 to 1,000,000, more preferably 50,000 to 400,000, even more preferably 80,000 to 250,000, and even more preferably 80,000 to 200,000. If the Mw of the thermoplastic elastomer (A) is 10,000 or more, the mechanical strength of the printing plate can be increased, and if it is 1,000,000 or less, the moldability of the printing plate can be increased. In this specification, the weight-average molecular weight refers to the weight-average molecular weight on a polystyrene basis, measured by gel permeation chromatography (GPC).

[0018] The vinyl content of the polymer block, which consists of structural units derived from the conjugated diene of the thermoplastic elastomer (A), is preferably 1 to 50 mol%, more preferably 5 to 50 mol%, even more preferably 5 to 40 mol%, even more preferably 5 to 30 mol%, and particularly preferably 10 to 30 mol%, from the viewpoint of the curability of the composition. Furthermore, from the viewpoint of the cold flow resistance of the composition, the vinyl content is preferably 40 to 80 mol%, more preferably 50 to 80 mol%, and even more preferably 50 to 75 mol%.

[0019] The content of thermoplastic elastomer (A) is preferably 40 to 87.9% by mass, more preferably 50 to 85% by mass, and even more preferably 60 to 80% by mass, based on the total amount of the photosensitive resin composition. If the content of thermoplastic elastomer (A) is 40% by mass or more, the tackiness of the composition before and after curing can be further reduced, and if it is 87.9% by mass or less, the flexibility of the composition can be increased.

[0020] [Liquid farnesene-based rubber (B)] The liquid farnesene-based rubber (B) used in this invention is a rubber that can be handled in liquid form. In this specification, "liquid" refers to a liquid farnesene-based rubber (B) whose melt viscosity measured at 38°C is 0.1 to 4,000 Pa·s. The melt viscosity is preferably 1 to 2,000 Pa·s, more preferably 2 to 1,000 Pa·s, even more preferably 10 to 750 Pa·s, and still more preferably 10 to 500 Pa·s. In another embodiment, the melt viscosity is preferably 0.3 to 2,000 Pa·s, more preferably 0.5 to 1,000 Pa·s, even more preferably 0.7 to 750 Pa·s, and still more preferably 0.7 to 500 Pa·s. The melt viscosity of the liquid farnesene-based rubber (B) is the value measured at 38°C using a Brookfield viscometer.

[0021] <Monomer unit (a)> Liquid farnesene-based rubber (B) is a liquid polymer containing monomer units (a) derived from farnesene (hereinafter sometimes simply referred to as "monomer units (a)"). The monomer unit (a) may be a monomer unit derived from α-farnesene, or a monomer unit derived from β-farnesene represented by the following formula (I), and may contain both monomer units derived from α-farnesene and monomer units derived from β-farnesene, but from the viewpoint of ease of manufacture, it is preferable to contain monomer units derived from β-farnesene. From the viewpoint of ease of manufacture, the content of monomer units derived from β-farnesene is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol% of monomer unit (a), that is, all monomer units of monomer unit (a) are derived from β-farnesene. The content of monomer unit (a) in the liquid farnesene-based rubber (B) is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more, from the viewpoint of further reducing the curability of the composition and the tackiness before and after curing. Furthermore, there is no particular upper limit to the content of monomer unit (a) in the liquid farnesene-based rubber (B), and it may be 100% by mass, less than 100% by mass, 99% by mass or less, 90% by mass or less, or 80% by mass or less. In one embodiment, the liquid farnesene-based rubber (B) contains other monomer units, and the content of monomer unit (a) is less than 100% by mass, preferably 99% by mass or less. In another embodiment, the content of monomer unit (a) in the liquid farnesene-based rubber (B) is 100% by mass.

[0022] [ka]

[0023] <Monomer unit (b)> The liquid farnesene-based rubber (B) may also be a liquid copolymer containing monomer units (a) and monomer units (b) derived from monomers other than farnesene (hereinafter sometimes simply referred to as "monomer unit (b)"). When the liquid farnesene rubber (B) is a copolymer of monomer unit (a) and monomer unit (b), the content of monomer unit (b) in the liquid farnesene rubber (B) is preferably 10 to 90% by mass, more preferably 20 to 70% by mass, and even more preferably 20 to 50% by mass. If the content of monomer unit (b) in the liquid farnesene rubber (B) is 10% by mass or more, the glass transition temperature can be lowered, and if it is 90% by mass or less, the viscosity decreases and handling can be improved.

[0024] Other monomers besides farnesene that can form liquid farnesene-based rubber (B) are not particularly limited as long as they are copolymerizable with farnesene. Examples of other monomers besides farnesene include aromatic vinyl compounds, conjugated diene compounds other than farnesene, acrylic acid and its derivatives, methacrylic acid and its derivatives, acrylamide and its derivatives, methacrylamide and its derivatives, and acrylonitrile. These other monomers besides farnesene may be used individually or in combination of two or more.

[0025] Examples of the above aromatic vinyl compounds include styrene and styrene derivatives such as α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, N,N-diethyl-4-aminoethylstyrene, 4-methoxystyrene, monochlorostyrene, and dichlorostyrene; and 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, and vinylpyridine. Among these, styrene and its derivatives are preferred, with styrene being more preferred. These aromatic vinyl compounds may be used individually or in combination of two or more.

[0026] Examples of the above-mentioned conjugated diene compounds include butadiene, isoprene, 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, myrcene, and chloroprene. Among these, butadiene, isoprene, and myrcene are preferred, and butadiene is more preferred. These conjugated dienes may be used individually or in combination of two or more.

[0027] Examples of the above-mentioned derivatives of acrylic acid include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, lauryl acrylate, stearyl acrylate, cyclohexyl acrylate, isobornyl acrylate, dicyclopentenyloxyethyl acrylate, tetraethylene glycol acrylate, tripropylene glycol acrylate, 4-hydroxybutyl acrylate, 3-hydroxy-1-adamantyl acrylate, tetrahydrofurfuryl acrylate, methoxyethyl acrylate, and N,N-dimethylaminoethyl acrylate. These derivatives of acrylic acid may be used individually or in combination of two or more.

[0028] Examples of the above-mentioned derivatives of methacrylic acid include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, dicyclopentanyl methacrylate, benzyl methacrylate, dicyclopentenyloxyethyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxy-1-adamantyl methacrylate, tetrahydrofurfuryl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and glycidylmethacrylamide methacrylate. These derivatives of methacrylic acid may be used individually or in combination of two or more.

[0029] Examples of acrylamide derivatives include dimethylacrylamide, acryloylmorpholine, isopropylacrylamide, diethylacrylamide, dimethylaminopropylacrylamide, dimethylaminopropylacrylamide methyl chloride quaternary salt, hydroxyethylacrylamide, and 2-acrylamide-2-methylpropanesulfonic acid. These acrylamide derivatives may be used individually or in combination of two or more.

[0030] Examples of derivatives of the above-mentioned methacrylamide include dimethylmethacrylamide, methacryloylmorpholine, isopropylmethacrylamide, diethylmethacrylamide, dimethylaminopropylmethacrylamide, and hydroxyethylmethacrylamide. These derivatives of methacrylamide may be used individually or in combination of two or more.

[0031] Among the monomers other than farnesene mentioned above, aromatic vinyl compounds and conjugated diene compounds other than farnesene are preferred, and conjugated diene compounds other than farnesene are more preferred.

[0032] The number-average molecular weight (Mn) of the liquid farnesene rubber (B) is preferably 10,000 to 150,000, more preferably 20,000 to 100,000, and even more preferably 25,000 to 80,000. When the Mn of the liquid farnesene rubber (B) is 10,000 or more, the curability of the composition can be improved and the tackiness before and after curing can be further reduced, and when it is 150,000 or less, the moldability of the composition is excellent. In another embodiment, the number-average molecular weight (Mn) of the liquid farnesene rubber (B) is preferably 7,000 to 150,000, more preferably 8,000 to 100,000, and even more preferably 8,500 to 80,000. If the Mn content of the liquid farnesene-based rubber (B) is 7,000 or higher, the curability of the composition can be improved and the tackiness before and after curing can be further reduced, and if it is 150,000 or lower, the moldability of the composition is excellent.

[0033] The molecular weight distribution (Mw / Mn) of the liquid farnesene rubber (B) is not particularly limited, but is preferably 1.0 to 2.0, more preferably 1.0 to 1.5, even more preferably 1.0 to 1.2, and even more preferably 1.0 to 1.1. When the Mw / Mn of the liquid farnesene rubber (B) is within the above range, the variation in the curability and tackiness of the composition can be suppressed. The number-average molecular weight and molecular weight distribution of liquid farnesene rubber (B) are determined by GPC measurement using the method described in the examples below, and are calculated on a polystyrene basis.

[0034] The glass transition temperature (Tg) of the liquid farnesene rubber (B) may vary depending on the bonding mode (microstructure), the content of farnesene-derived monomer units (a) and other monomer units other than farnesene (b) used as needed, but is preferably -65°C or lower, more preferably -70°C or lower, and even more preferably -75°C or lower. When the Tg of the liquid farnesene rubber (B) is -65°C or lower, an improvement in the high-speed printability of the printing plate can be expected when the composition of the present invention is used as a printing plate. Furthermore, there is no particular lower limit to the Tg of the liquid farnesene rubber (B), but is preferably -100°C or higher, more preferably -90°C or higher, and even more preferably -85°C or higher. In another embodiment, the glass transition temperature (Tg) of the liquid farnesene rubber (B) is preferably -60°C or lower, more preferably -65°C or lower, even more preferably -70°C or lower, and may be -75°C or lower. When the Tg of the liquid farnesene rubber (B) is -60°C or lower, an improvement in the high-speed printability of the printing plate can be expected when the composition of the present invention is used as a printing plate. Furthermore, there is no particular lower limit to the Tg of the liquid farnesene rubber (B), but it is preferably -100°C or higher, more preferably -90°C or higher, and even more preferably -85°C or higher. The Tg of liquid farnesene-based rubber (B) is determined by differential scanning calorimetry, and more specifically by the method described in the examples below.

[0035] The vinyl content of the monomer unit (a) of the liquid farnesene rubber (B) is preferably 0.5 to 70 mol%, more preferably 1 to 60 mol%, even more preferably 1 to 50 mol%, even more preferably 1 to 40 mol%, even more preferably 3 to 30 mol%, and particularly preferably 5 to 15 mol%, from the viewpoint of the curability of the composition and the high-speed printability of the printing plate derived from the above-mentioned Tg. In this specification, "vinyl content of monomer unit (a)" refers to the content of monomer units derived from farnesene that exclude the 1,13 linkage shown in formula (II) below.

[0036] [ka]

[0037] The vinyl content of the liquid farnesene rubber (B) is preferably 5 to 80 mol%, more preferably 5 to 60 mol%, even more preferably 5 to 50 mol%, and even more preferably 5 to 45 mol%, from the viewpoint of the curability of the composition and the high-speed printability of the printing plate derived from the above-mentioned Tg. In this specification, "vinyl content of liquid farnesene-based rubber (B)" means the sum of the vinyl content of the farnesene-derived monomer unit (a) and the vinyl content of other monomer units (b) other than farnesene. The vinyl content of liquid farnesene-based rubber (B) is determined by calculating the vinyl content of each of the farnesene-derived monomer unit (a) and other monomer units (b) other than farnesene, and then summing them up. The vinyl content of the farnesene-derived monomer unit (a) and the vinyl content of other monomer units (b) other than farnesene are described in the examples below. 1 This can be measured using a method employing H-NMR.

[0038] The content of liquid farnesene rubber (B) is preferably 10 to 40% by mass, more preferably 10 to 35% by mass, and even more preferably 10 to 30% by mass, based on the total amount of the photosensitive resin composition. When the content of liquid farnesene rubber (B) is 10% by mass or more, the viscosity of the composition during molding can be reduced, improving processability, and the flexibility of the resulting molded article can be improved. The molded article can preferably be used as a printing plate. Furthermore, when the content of liquid farnesene rubber (B) is 40% by mass or less, the tackiness of the molded article obtained by molding the composition before and after curing can be further reduced. This characteristic is particularly important in embodiments in which the molded article is used as a printing plate.

[0039] [Ethylene-unsaturated compounds (C)] The ethylenically unsaturated compound (C) used in the present invention includes esters of acrylic acid, methacrylic acid, fumaric acid, maleic acid, acrylamide and methacrylamide derivatives, allyl esters, styrene and its derivatives, N-substituted maleimide compounds, etc. Specific examples include diacrylates and dimethacrylates of alkanediols such as hexanediol and nonanediol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, butylene glycol diacrylates and dimethacrylates, trimethylolpropane tri(meth)acrylate, dimethylol tricyclodecane di(meth)acrylate, isobolonyl(meth)acrylate, lauryl(meth)acrylate, phenoxypolyethylene glycol(meth)acrylate, pentaerythritol(meth)acrylate, N,N Examples include hexamethylenebisacrylamide and methacrylamide, styrene, vinyltoluene, divinylbenzene, diacrylphthalate, triallyl cyanurate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, distearyl fumarate, butyloctyl fumarate, diphenyl fumarate, dibenzyl fumarate, dibutyl maleate, dioctyl maleate, bis(3-phenylpropyl) fumarate, dilauryl fumarate, dibehenyl fumarate, N-laurylmaleimide, etc. These may be used individually or in combination of two or more types.

[0040] Among these, alkanediol di(meth)acrylate is preferred as the ethylenically unsaturated compound (C) from the viewpoint of curing properties.

[0041] The content of ethylenically unsaturated compound (C) is preferably 2 to 30% by mass, more preferably 2 to 20% by mass, and even more preferably 3 to 15% by mass, based on the total amount of the photosensitive resin composition. When the content of ethylenically unsaturated compound (C) is 2% by mass or more, the curability is improved, and the ability to form fine dots and characters on the printing plate can be improved, while when it is 30% by mass or less, the flexibility can be improved.

[0042] [Photoinitiator (D)] As the photoinitiator (D) used in the present invention, known photoinitiators such as aromatic ketones and benzoin ethers can be used, for example, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methylpropiophenone, diethoxyacetophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropanone, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropanone, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin Examples include phenyl ether, benzyl dimethyl ketal, benzophenone, benzoyl benzoic acid, methyl benzoyl benzoate, 4-phenylbenzophenone, 4-methoxybenzophenone, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, methylphenyl glyoxylate, benzyl, camphorquinone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. The photoinitiator (D) may be used alone or in combination of two or more types. In particular, from the viewpoint of curability, benzyldimethyl ketal, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide are preferred, with benzyldimethyl ketal being more preferred.

[0043] Furthermore, commercially available products such as "Irgacure 184", "Irgacure 127", "Irgacure 149", "Irgacure 261", "Irgacure 369", "Irgacure 500", "Irgacure 651", "Irgacure 754", "Irgacure 784", "Irgacure 819", "Irgacure 907", "Irgacure 1116", "Irgacure 1173", "Irgacure 1664", "Irgacure 1700", "Irgacure 1800", "Irgacure 1850", "Irgacure 2959", "Irgacure 4043", "Darocure (registered trademark; hereinafter omitted) 1173", and "Darocure MBF" (all manufactured by BASF) are preferably used as photoinitiators (D).

[0044] The content of the photoinitiator (D) is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass, relative to the total amount of the photosensitive resin composition. If the content of the photoinitiator (D) is 0.1% by mass or more, the ability to form fine dots and characters on the printing plate can be improved, and if it is 10% by mass or less, the transmittance of active light such as ultraviolet light can be improved.

[0045] [Other ingredients] In addition to the thermoplastic elastomer (A), liquid farnesene rubber (B), ethylenically unsaturated compound (C), and photoinitiator (D) described above, the photosensitive resin composition of the present invention may also contain other components such as antioxidants, plasticizers, fillers, colorants, thermal polymerization inhibitors, ultraviolet absorbers, anti-halation agents, and light stabilizers.

[0046] The content of the above-mentioned other components is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 0.1 to 50% by mass, more preferably 0.5 to 40% by mass, and even more preferably 0.5 to 30% by mass, based on the total amount of the photosensitive resin composition.

[0047] In the total amount of the photosensitive resin composition of the present invention, the total content of thermoplastic elastomer (A), liquid farnesene rubber (B), ethylenically unsaturated compound (C), and photoinitiator (D) is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may be 100% by mass or less, 98% by mass or less, or 96% by mass or less.

[0048] (Method for producing a photosensitive resin composition) There are no particular limitations on the method for producing the photosensitive resin composition of the present invention, and a method that can uniformly mix a thermoplastic elastomer (A), a liquid farnesene rubber (B), an ethylenically unsaturated compound (C), a photoinitiator (D), and the other components mentioned above can be preferably employed. Mixing is usually preferably carried out by melt-kneading using a single-screw extruder, twin-screw extruder, kneader, Banbury mixer, etc. The mixing temperature is preferably 100 to 200°C, and more preferably 120 to 180°C. The photosensitive resin composition after kneading can be formed into a sheet of a desired thickness by calendering, pressing, or extrusion molding. The molding temperature is preferably 100 to 200°C, and more preferably 120 to 180°C. The photosensitive resin composition of the present invention can also be used as a layer constituting a laminate.

[0049] (Physical properties of photosensitive resin compositions) The photosensitive resin composition of the present invention preferably exhibits lower tackiness before curing compared to comparable photosensitive resin compositions containing liquid farnesene rubber (B) substitutes. This lower tackiness before curing allows for easy removal of a negative film after image exposure, even when placed directly on the photosensitive layer made of the photosensitive resin composition, enabling reuse of the negative film. Furthermore, the photosensitive resin composition of the present invention preferably exhibits lower tackiness after curing compared to comparable photosensitive resin compositions containing liquid farnesene rubber (B) substitutes. This lower tackiness after curing reduces stickiness in flexographic printing plates having a photosensitive layer made of the photosensitive resin composition, suppressing dust adhesion and tearing of the printed material during printing, resulting in superior printability. The tackiness of the above photosensitive resin composition before and after curing can be measured by the method described in the examples.

[0050] The photosensitive resin composition according to one embodiment preferably has a tackiness of 9.5 N or less at 25°C before curing, more preferably 7.5 N or less, even more preferably 6.5 N or less, even more preferably 6.0 N or less, and particularly preferably 5.5 N or less. In this embodiment, the photosensitive resin composition preferably comprises a thermoplastic elastomer (A) containing a styrene-butadiene-styrene block copolymer, more preferably a thermoplastic elastomer (A) containing a styrene-butadiene-styrene block copolymer, and a liquid farnesene-based rubber (B) containing monomer units (a) and monomer units (b). There is no particular limit to the lower limit of the tackiness at 25°C before curing, but for example, it is 0.1 N or more. When the tackiness at 25°C before curing is 9.5 N or less, the above-mentioned effects are more pronounced.

[0051] Furthermore, the photosensitive resin composition according to the above-described embodiment preferably has a tackiness of 3.0 N or less, more preferably 2.5 N or less, and even more preferably 2.0 N or less at 25°C after curing. There is no particular limit to the lower limit of the tackiness at 25°C after curing, but for example, it is 0.1 N or more. The above-mentioned effects are more pronounced when the tackiness at 25°C after curing is 3.0 N or less.

[0052] In another embodiment, the photosensitive resin composition has a tackiness at 25°C before curing preferably less than 14.3 N, more preferably 13.5 N or less, and even more preferably 13.3 N or less. In this other embodiment, the photosensitive resin composition preferably comprises a thermoplastic elastomer (A) containing a styrene-isoprene-styrene block copolymer, and more preferably, the thermoplastic elastomer (A) contains a styrene-isoprene-styrene block copolymer, and the monomer unit (a) content in the liquid farnesene rubber (B) is 100% by mass. There is no particular limit to the lower limit of the tackiness at 25°C before curing, but for example, it is 0.1 N or more. When the tackiness at 25°C before curing is less than 14.3 N, the above-mentioned effects are more pronounced.

[0053] Furthermore, the photosensitive resin composition according to the other embodiment described above preferably has a tackiness of less than 6.3 N at 25°C after curing, more preferably 6.2 N or less, and even more preferably 6.1 N or less. There is no particular limit to the lower limit of the tackiness at 25°C after curing, but for example, it is 0.1 N or more. The above-mentioned effects are more pronounced when the tackiness at 25°C after curing is less than 6.3 N.

[0054] The cured product of the photosensitive resin composition of the present invention preferably exhibits a low extractability of components from a solvent, such as toluene. Due to this low extractability, the flexographic printing plate having a photosensitive layer made of such a photosensitive resin composition exhibits excellent printability stability because changes in physical properties over time are suppressed. For example, it can be expected to have excellent long-run performance when used for a long time and excellent storage stability when stored for a long period of time. More preferably, the cured product of the photosensitive resin composition of the present invention exhibits a low extractability of components from a solvent, such as toluene, while also exhibiting the aforementioned low tackiness before and after curing. Furthermore, the extraction rate of the liquid farnesene-based rubber (B) from the cured product of the above photosensitive resin composition can be measured by the method described in the examples.

[0055] The cured product of the photosensitive resin composition according to the above embodiment preferably has an extraction rate of liquid farnesene rubber (B) of 15.0% by mass or less, more preferably 10.0% by mass or less, and even more preferably 8.0% by mass or less, after immersion in toluene at 25°C for 48 hours. When the above extraction rate is 15.0% by mass or less, the above-mentioned effects are more pronounced.

[0056] The cured product of the photosensitive resin composition according to the other embodiment described above preferably has an extraction rate of liquid farnesene rubber (B) of 20.0% by mass or less, more preferably 19.0% by mass or less, and even more preferably 18.0% by mass or less, after immersion in toluene at 25°C for 48 hours. When the extraction rate is 20.0% by mass or less, the cured product of the photosensitive resin composition according to this other embodiment tends to exhibit a low extraction rate while exhibiting the aforementioned effect of low tackiness before and after curing.

[0057] The cured product of the photosensitive resin composition of the present invention preferably tends to have a lower glass transition temperature (Tg) compared to the cured product of a photosensitive resin composition containing a comparable liquid farnesene rubber (B) substitute. This lower glass transition temperature (Tg) allows for improved high-speed printing performance in flexographic printing plates having a photosensitive layer made from such a photosensitive resin composition. The Tg of the cured product of the above photosensitive resin composition can be measured by the method described in the examples.

[0058] The cured product of the photosensitive resin composition according to the above-described embodiment preferably has a glass transition temperature (Tg) of -80°C or lower, more preferably -84°C or lower, and even more preferably -86°C or lower. When the Tg is -80°C or lower, the above-mentioned effects are more pronounced.

[0059] The cured product of the photosensitive resin composition according to the other embodiment described above preferably has a glass transition temperature (Tg) of -57°C or lower, more preferably -59°C or lower, and even more preferably -61°C or lower. When the Tg is -57°C or lower, the above-mentioned effects are more pronounced.

[0060] [Flexographic printing version] The flexographic printing plate of the present invention has a photosensitive layer made of the above-mentioned photosensitive resin composition. For example, a flexographic printing plate can be obtained by placing a sheet of the above-mentioned photosensitive resin composition on a support, pressing the support and the sheet of the photosensitive resin composition together by roll lamination, and then applying a heat press to form a photosensitive layer on the support.

[0061] The thickness of the photosensitive layer is typically 0.5 to 7 mm, preferably 0.5 to 3.5 mm. The thickness of the printing plate is typically 0.5 to 7.0 mm, preferably 0.5 to 3.5 mm. The thickness of the printing plate can be changed depending on the material to be printed. If it is necessary to reduce the thickness of the printing plate depending on the material to be printed, for example, if it is required to be 3.0 mm or less, the amount of each component in the photosensitive resin composition may be changed, or, referring to the other embodiment described above, the thermoplastic elastomer (A) in the photosensitive resin composition may contain a styrene-isoprene-styrene block copolymer. The hardness of the above-mentioned printing plate is typically 28 to 74 on the Type A hardness scale, preferably 30 to 65. The hardness of the printing plate can be measured using a Type A hardness tester in accordance with JIS K6253-3:2012. The hardness of the printing plate can be changed depending on the material to be printed on. If it is necessary to increase the hardness of the printing plate depending on the material to be printed on, for example, if it is required to have a Type A hardness of 60 or higher when the thickness of the printing plate is 3.0 mm or less, the amount of each component in the photosensitive resin composition may be changed, or, referring to the other embodiment described above, the thermoplastic elastomer (A) in the photosensitive resin composition may include a styrene-isoprene-styrene block copolymer. The other embodiment described above is particularly suitable when the thickness of the printing plate is small and the hardness is high.

[0062] A common method for producing flexographic printing plates from components for flexographic printing plates involves first exposing the entire surface of the support to ultraviolet light (back exposure), creating a thin, uniform hardened layer at the interface between the photosensitive layer and the support, and then exposing the surface of the photosensitive layer to ultraviolet light (relief exposure) through a negative film covering the top of the photosensitive layer. After that, the unexposed areas of the photosensitive layer are washed away with a developer, or removed by absorption with an absorption layer after heating and melting, and then subjected to post-processing exposure.

[0063] To change the surface tension of the plate surface, the image exposure may be performed by first exposing it with ultraviolet light in the wavelength range of 200-300 nm, followed by exposure with ultraviolet light in the wavelength range of 310-400 nm. Exposure from the negative film side (relief exposure) and exposure from the support side (back exposure) may be performed in either order, or both may be performed simultaneously.

[0064] Examples of exposure light sources include high-pressure mercury lamps, ultraviolet fluorescent lamps, carbon arc lamps, xenon lamps, or diode lamps. Examples of developing solvents used to develop unexposed areas include esters such as heptyl acetate and 3-methoxybutyl acetate, petroleum fractions, hydrocarbons such as toluene and decalin, and chlorinated organic solvents such as tetrachloroethylene, mixed with alcohols such as propanol, butanol, and pentanol. Unexposed areas are washed out with developing solvent by spraying from a nozzle or by brushing with a brush. As a post-processing exposure, it is common to irradiate the surface with light with a wavelength of 300 nm or less. If necessary, light with a wavelength greater than 300 nm may also be used. [Examples]

[0065] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0066] The components used in the examples and comparative examples are as follows: [Thermoplastic elastomer (A)] • Thermoplastic elastomer (A-1): D-1102JS (trade name, manufactured by Kraton, styrene-butadiene-styrene block copolymer, Mw=120,000, vinyl content=11 mol%, styrene content=30% by mass) • Thermoplastic elastomer (A-2): Quintac (registered trademark) 3421 (product name, manufactured by Zeon Corporation, styrene-isoprene-styrene block copolymer, Mw = 200,000, vinyl content = 7 mol%, styrene content = 14% by mass)

[0067] [Liquid farnesene-based rubber (B)] • Liquid polyfarnesene butadiene copolymer (B-1): Liquid polyfarnesene butadiene copolymer (B-1) produced in Production Example 1 described below. • Liquid polyfarnesene butadiene copolymer (B-2): Liquid polyfarnesene butadiene copolymer (B-2) produced in Production Example 2 described below. • Liquid polyfarnesene butadiene copolymer (B-3): Liquid polyfarnesene butadiene copolymer (B-3) produced in Production Example 3 described below. • Liquid polyfarnesene (B-4): Liquid polyfarnesene (B-4) produced in Production Example 7 described below.

[0068] [Liquid polybutadiene] • Liquid polybutadiene (b-1): Liquid polybutadiene (b-1) produced in Production Example 4 described below. • Liquid polybutadiene (b-2): Liquid polybutadiene (b-2) produced in Production Example 5 described below. • Liquid polybutadiene (b-3): Liquid polybutadiene (b-3) produced in Production Example 6 described below.

[0069] [Ethylene-unsaturated compounds (C)] • Ethylene unsaturated compound (C-1): HDDA (trade name, manufactured by Tokyo Chemical Industry Co., Ltd., 1,6-hexanediol diacrylate)

[0070] [Photoinitiator (D)] • Photoinitiator (D-1): Irgacure 651 (product name, manufactured by BASF)

[0071] [Other ingredients] • Antioxidant: BHT (product name, manufactured by Kawaguchi Chemical Industry Co., Ltd., dibutylhydroxytoluene)

[0072] <Manufacturing example> [Procedure for purifying farnesene] β-farnesene (purity 97.6% by mass, manufactured by Amyris Biotechnology) was purified using a 3 Å molecular sieve and then distilled under a nitrogen atmosphere to remove hydrocarbon impurities such as zingiberene, bisabolene, farnesene epoxide, farnesol isomers, E,E-farnesol, squalene, ergosterol, and several dimers of farnesene, thereby purifying β-farnesene.

[0073] [Production Example 1] Liquid polyfarnesene butadiene copolymer (B-1) In a nitrogen-purged and dried pressure vessel, 1140 g of cyclohexane was charged as the solvent and 56.2 g of sec-butyllithium (10.5% by mass cyclohexane solution) as a polymerization initiator. After raising the temperature to 50°C, a pre-prepared mixture of 1080 g of β-farnesene and 720 g of butadiene was added and polymerization was carried out for 1 hour. The resulting polymerization reaction solution was treated with methanol and washed with water. After washing, the polymerization reaction solution and water were separated and dried at 70°C for 12 hours to produce liquid polyfarnesene butadiene copolymer (B-1), a random copolymer containing 60% by mass of farnesene units and 40% by mass of butadiene units.

[0074] [Production Example 2] Liquid polyfarnesene butadiene copolymer (B-2) In a nitrogen-purged and dried pressure vessel, 267 g of cyclohexane was charged as the solvent and 7.4 g of sec-butyllithium (10.5% by mass cyclohexane solution) as the polymerization initiator. After raising the temperature to 50°C, a pre-prepared mixture of 160 g of β-farnesene and 240 g of butadiene was added and polymerization was carried out for 2 hours. The resulting polymerization reaction solution was treated with methanol and washed with water. After washing, the polymerization reaction solution and water were separated and dried at 70°C for 12 hours to produce liquid polyfarnesene butadiene copolymer (B-2), a random copolymer containing 40% by mass of farnesene units and 60% by mass of butadiene units.

[0075] [Production Example 3] Liquid polyfarnesene butadiene copolymer (B-3) In a nitrogen-purged and dried pressure vessel, 267 g of cyclohexane was charged as the solvent and 9.3 g of sec-butyllithium (10.5% by mass cyclohexane solution) as the polymerization initiator. After raising the temperature to 50°C, a pre-prepared mixture of 80 g of β-farnesene and 320 g of butadiene was added and polymerization was carried out for 2 hours. The resulting polymerization reaction solution was treated with methanol and washed with water. After washing, the polymerization reaction solution and water were separated and dried at 70°C for 12 hours to produce liquid polyfarnesene butadiene copolymer (B-3), a random copolymer containing 20% ​​by mass of farnesene units and 80% by mass of butadiene units.

[0076] [Manufacturing Example 4] Liquid polybutadiene (b-1) In a nitrogen-purged and dried pressure vessel, 400 g of hexane was charged as the solvent, and 48.4 g of n-butyllithium (17% by mass hexane solution) was charged as the initiator. 5.4 g of N,N,N',N'-tetramethylethylenediamine was then charged as the polar compound. After raising the temperature to 50°C, 400 g of butadiene was added and polymerization was carried out for 1 hour. The resulting polymerization reaction solution was treated with methanol and washed with water. After washing, the polymerization reaction solution and water were separated and dried at 70°C for 12 hours to produce liquid polybutadiene (b-1).

[0077] [Manufacturing Example 5] Liquid polybutadiene (b-2) In a nitrogen-purged and dried pressure vessel, 400 g of hexane was charged as the solvent and 11.2 g of n-butyllithium (17% by mass hexane solution) as the initiator. After raising the temperature to 50°C, 400 g of butadiene was added and polymerization was carried out for 1 hour. The resulting polymerization reaction solution was treated with methanol and washed with water. After washing, the polymerization reaction solution and water were separated and dried at 70°C for 12 hours to produce liquid polybutadiene (b-2).

[0078] [Manufacturing Example 6] Liquid polybutadiene (b-3) In a nitrogen-purged and dried pressure vessel, 267 g of hexane was charged as the solvent, and 60.5 g of n-butyllithium (17% by mass hexane solution) was charged as the initiator. 2.6 g of N,N,N',N'-tetramethylethylenediamine was then charged as the polar compound. After raising the temperature to 50°C, 400 g of butadiene was added and polymerization was carried out for 1 hour. The resulting polymerization reaction solution was treated with methanol and washed with water. After washing, the polymerization reaction solution and water were separated and dried at 70°C for 12 hours to produce liquid polybutadiene (b-3).

[0079] [Manufacturing Example 7] Liquid polyfarnesene (B-4) In a nitrogen-purged and dried pressure vessel, 400 g of cyclohexane was charged as the solvent and 29.8 g of sec-butyllithium (10.5% by mass cyclohexane solution) as the polymerization initiator. After raising the temperature to 50°C, 400 g of pre-prepared β-farnesene was added and polymerization was carried out for 2 hours. The resulting polymerization reaction solution was treated with methanol and washed with water. After washing, the polymerization reaction solution and water were separated and dried at 70°C for 12 hours to produce liquid polyfarnesene (B-4).

[0080] [Measurement of liquid farnesene-based rubber (B) and liquid polybutadiene] The liquid polyfarnesene butadiene copolymers (B-1) to (B-3), liquid polyfarnesene (B-4), and liquid polybutadiene (b-1) to (b-3), (hereinafter also referred to as liquid polymers), obtained in Production Examples 1 to 7, were evaluated for their physical properties according to the method described below. The results are shown in Table 1. [Weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn)] The Mw, Mn, and Mw / Mn of the liquid polymer were determined by GPC (gel permeation chromatography) using standard polystyrene-based molecular weight. The measurement equipment and conditions are as follows. • Equipment: GPC8020 GPC system manufactured by Tosoh Corporation • Separation column: "TSKgel G4000HXL" manufactured by Tosoh Corporation • Detector: "RI-8020" manufactured by Tosoh Corporation • Eluent: Tetrahydrofuran ·Eluent flow rate: 1.0ml / min • Sample concentration: 5 mg / 10 ml Column temperature: 40℃

[0081] [Vinyl content] A solution prepared by dissolving 50 mg of liquid polymer in 1 ml of deuterated chloroform (CDCl3) was prepared by Bruker. 1 Measurements were taken using 1H-NMR (400MHz) with 512 integration cycles. The vinyl content derived from farnesene was determined based on the cumulative values ​​of each part of the chart obtained by measurement, according to the method described below. 4.45~4.85 ppm portion: Part A (spectrum derived from the vinyl structure of farnesene units) 4.94~5.22 ppm portion: Part B (synthetic spectrum of the vinyl structure of farnesene units and the spectrum of the 1,13-bond) 4.85~4.94 ppm portion: Partial C (spectrum derived from the vinyl structure of butadiene units) 5.22~5.65 ppm portion: Part D (synthetic spectrum of the vinyl structure of the butadiene unit and the spectrum of the 1,4 bond)

[0082] The vinyl content of liquid polyfarnesene butadiene copolymers (B-1) to (B-3) was calculated based on the following formula. {Vinyl content (from farnesene)} = Integral value of part B / 2 / {Integral value of part B / 2 + (Integral value of part B - Integral value of part A) / 3 + Integral value of part C / 2 + [Integral value of part D - (Integral value of part C / 2)] / 2} × 100 {Vinyl content (derived from butadiene)} = Integral value of part C / 2 / {Integral value of part C / 2 + [Integral value of part D - (Integral value of part C / 2)] / 2 + Integral value of part B / 2 + (Integral value of part B - Integral value of part A) / 3} × 100 Vinyl content of liquid farnesene-based rubber (B) = {Vinyl content (derived from farnesene)} + {Vinyl content (derived from butadiene)}

[0083] The vinyl content of liquid polyfarnesene (B-4) was calculated based on the following formula. {Vinyl content (derived from farnesene)} = Integral value of part B / 2 / {Integral value of part B / 2 + (Integral value of part B - Integral value of part A) / 3} × 100

[0084] The vinyl content of liquid polybutadiene (b-1) to (b-3) was calculated based on the following formula. {Vinyl content (derived from butadiene)} = Integral value of part C / 2 / {Integral value of part C / 2 + [Integral value of part D - (Integral value of part C / 2)] / 2} × 100

[0085] [Glass transition temperature (Tg)] 10 mg of liquid polymer was placed in an aluminum open pan, and an aluminum lid was placed on top and crimped with a sample sealer. A thermogram was measured by differential scanning calorimetry (DSC) at a heating rate of 10°C / min, and the peak value of the DSC was defined as the glass transition temperature (Tg). The measurement equipment and conditions are as follows. [Measurement device and measurement conditions] • Equipment: Seiko Instruments Inc. Differential Scanning Calorimeter "DSC6200" • Cooling device: Cooling controller manufactured by Seiko Instruments Inc. • Detection unit: Heat flow type • Sample weight: 10 mg • Heating rate: 10°C / min • Cooling conditions: 10°C / min. After cooling, the temperature was kept constant at -130°C for 3 minutes before starting the heating process. • Reference container: Aluminum • Reference weight: 0mg

[0086] [Melting viscosity (38°C)] The melt viscosity of the liquid polymer at 38°C was measured using a Brookfield viscometer (manufactured by BROOKFIELD ENGINEERING LABS. INC.).

[0087] [Table 1]

[0088] <First Example: Examples 1-1 to 1-5, and Comparative Examples 1-1 to 1-3> The components listed in Table 2, in terms of type and amount, were kneaded in a mixer set to a temperature of 140°C to prepare a photosensitive resin composition. The obtained photosensitive resin composition was covered on both sides with a polyester film that would form a cover sheet with a thickness of 100 μm, and molded using a press machine set to a temperature of 140°C to obtain a sheet with a thickness of 2 mm (hereinafter also referred to as the uncured sheet). Next, the obtained uncured sheet was subjected to UV irradiation using a UV irradiator (Heraeus; mercury xenon lamp) at an irradiance of 500 mJ / cm². 2 Total luminous intensity 8000 mJ / cm² 2 Under these conditions, ultraviolet light was irradiated to obtain a sheet with a thickness of 2 mm after curing (hereinafter also referred to as the cured sheet).

[0089] [Evaluation Method] The physical properties of the uncured sheets and cured sheets obtained in the above examples and comparative examples were evaluated according to the method described below. The results are shown in Table 2.

[0090] (1) Tuck The uncured and cured sheets were cut into 2cm x 10cm pieces. The cover sheets were peeled off the uncured and cured sheets, and the tackiness (stickiness) was measured using a Picmatack Tester (manufactured by Toyo Seiki Co., Ltd.) by bringing the stainless steel plate into contact with the surfaces of the uncured and cured sheets at a speed of 10mm / min for 4 seconds, and then peeling the uncured and cured sheets perpendicular to the surface of the stainless steel plate at a speed of 10mm / min.

[0091] (2) Extraction rate The cured sheets obtained in the above examples and comparative examples were punched out to a diameter of 32 mm, the cover sheet was peeled off, and the sheets were immersed in 100 ml of toluene at 25°C for 48 hours. The extraction rate of the liquid polymer extracted from the cured sheets was then calculated from the weight change.

[0092] (3) Glass transition temperature (Tg) A 10 mg sample of the cured sheet was placed in an aluminum open pan, an aluminum lid was placed on top, and the pan was crimped with a sample sealer. A thermogram was measured by differential scanning calorimetry (DSC) at a heating rate of 10°C / min, and the peak value of the DSC was defined as the glass transition temperature (Tg). The measurement equipment and conditions were the same as those used for measuring the glass transition temperature of the liquid polymer described above.

[0093] [Table 2]

[0094] Table 2 shows that the photosensitive resin compositions of Examples 1-1 to 1-5 exhibit low tackiness before and after curing, low extraction rate of the liquid polymer after curing, and a low glass transition temperature of the sheet after curing.

[0095] <Second Example: Examples 2-1 to 2-2, and Comparative Example 2-1> The components listed in Table 3, in terms of type and amount, were kneaded in a mixer set to a temperature of 140°C to prepare a photosensitive resin composition. The obtained photosensitive resin composition was covered on both sides with a polyester film that would form a 100 μm thick cover sheet, and then molded using a press machine set to a temperature of 140°C to obtain a 2 mm thick sheet (uncured sheet). Next, the obtained uncured sheet was subjected to UV irradiation using a UV irradiator (Heraeus; mercury xenon lamp) at an irradiance of 500 mJ / cm². 2 Total luminous intensity 8000 mJ / cm² 2 Under these conditions, ultraviolet light was irradiated to obtain a sheet (cured sheet) with a thickness of 2 mm after curing.

[0096] [Evaluation Method] The uncured sheets and cured sheets obtained in the above examples and comparative examples were evaluated for their physical properties ((1) tackiness, (2) extraction rate, and (3) glass transition temperature (Tg)) according to the same method as shown in the first example. The results are shown in Table 3.

[0097] [Table 3]

[0098] Table 3 shows that the photosensitive resin compositions of Examples 2-1 to 2-2 can provide photosensitive resin compositions with low tackiness before and after curing while maintaining a low extraction rate after curing. Furthermore, Table 3 shows that the photosensitive resin compositions of Examples 2-1 to 2-2 also have a low glass transition temperature of the sheet after curing. [Industrial applicability]

[0099] The photosensitive resin composition of the present invention has low tackiness before curing, so even if a negative film is placed directly on the photosensitive layer made of the photosensitive resin composition, the negative film can be easily peeled off after image exposure, and the negative film can be reused. Furthermore, because the photosensitive resin composition of the present invention has low tackiness after curing, a printing plate having a photosensitive layer made of the photosensitive resin composition has reduced stickiness, which suppresses the adhesion of dust during printing and the tearing of the printed material, resulting in excellent printability. In addition, because the photosensitive resin composition of the present invention tends to have a low extraction rate of liquid polymer after curing, a printing plate having a photosensitive layer made of the photosensitive resin composition has excellent printability stability because the change in physical properties over time is suppressed.Therefore, the photosensitive resin composition of this embodiment is suitably used in flexographic printing plates.

Claims

1. A photosensitive resin composition comprising a thermoplastic elastomer (A), a liquid farnesene rubber (B), an ethylenically unsaturated compound (C), and a photoinitiator (D), Liquid farnesene-based rubber (B) is a liquid polymer containing monomer units (a) derived from farnesene, The aforementioned monomer unit (a) derived from farnesene contains a monomer unit derived from β-farnesene represented by the following formula (I), 【Chemistry 1】 The content of monomer units derived from β-farnesene in the monomer unit (a) is 80 mol% or more. Photosensitive resin composition.

2. The content of monomer units derived from β-farnesene in the monomer unit (a) is 100 mol%, The photosensitive resin composition according to claim 1.

3. The photosensitive resin composition according to claim 1 or 2, wherein the thermoplastic elastomer (A) is at least one selected from the group consisting of styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-(ethylene-butylene)-styrene block copolymer, and styrene-(ethylene-propylene)-styrene block copolymer.

4. The photosensitive resin composition according to claim 1 or 2, wherein the content of the farnesene-derived monomer unit (a) in the liquid farnesene-based rubber (B) is 10% by mass or more.

5. The photosensitive resin composition according to claim 1 or 2, wherein the number average molecular weight of the liquid farnesene-based rubber (B) is 7,000 to 150,000.

6. The photosensitive resin composition according to claim 1 or 2, wherein the glass transition temperature of the liquid farnesene-based rubber (B) is -60°C or lower.

7. The photosensitive resin composition according to claim 1 or 2, wherein the vinyl content of the liquid farnesene-based rubber (B) is 5 to 80 mol%.

8. The photosensitive resin composition according to claim 1 or 2, wherein the thermoplastic elastomer (A) is at least one selected from the group consisting of styrene-butadiene-styrene block copolymer and styrene-isoprene-styrene block copolymer.

9. The photosensitive resin composition according to claim 8, wherein the thermoplastic elastomer (A) comprises a styrene-butadiene-styrene block copolymer.

10. The photosensitive resin composition according to claim 8, wherein the thermoplastic elastomer (A) comprises a styrene-isoprene-styrene block copolymer.

11. The photosensitive resin composition according to claim 1 or 2, wherein the content of the thermoplastic elastomer (A) is 40 to 87.9% by mass, the content of the liquid farnesene rubber (B) is 10 to 40% by mass, the content of the ethylenically unsaturated compound (C) is 2 to 30% by mass, and the content of the photoinitiator (D) is 0.1 to 10% by mass, based on the total amount of the photosensitive resin composition.

12. A flexographic printing plate having a photosensitive layer made of the photosensitive resin composition according to claim 1 or 2.

13. A laminate having a layer made of the photosensitive resin composition according to claim 1 or 2.

Images